Dermatophytes are molds, closely related to Aspergillus and the dimorphic fungi. These molds cause infections within the skin and nails, including athlete's foot, the most common fungal infection worldwide. In the United States, the economic impact of athlete's foot alone on the health care system is estimated to exceed $400 million a year. Similarly, fungal infection of the head is a frequent pediatric infection in major urban centers in the U.S. and worldwide, and is especially common in socio-economically depressed populations. In a recent study, 22-50% of children in a U.S. daycare exhibited symptoms of dermatophytic scalp infection. The dermatophytes remain under-studied and under-funded. Recent genome sequencing and EST analysis of the dermatophytes will enable researchers to generate hypotheses concerning the dermatophytes with the ultimate goal to develop methods for the detection (diagnostics), treatment (drugs), and prevention (vaccines or prophylaxis) of dermatophyte infections. A standard method for testing hypotheses is to alter the genotype of the fungal cell and then assess the resulting phenotype. However, the tools for altering the genotype and assessing the phenotype are severely limited for dermatophytes. The objective of this proposal is to develop a molecular toolbox that will allow researchers to test hypotheses relating to dermatophyte pathogenicity. The specific aims of the proposal are as follows: Aim 1 - To develop techniques for altering the dermatophyte genotype, using split markers to maximize homologous recombination, and Agrobacterium tumefaciens transformation for random mutagenesis and gene expression control. Aim 2 - To evaluate alternate host pathogen models for assessing dermatophyte phenotypes. Human skin "rafts" will be used to study the interactions of the fungus with differentiated keratinocytes. Dermatophyte infections will also be tested in Galleria mellonella, a wax moth larvae which is currently in use for other fungal infections. When completed, these aims will provide hypothesis-testing tools that are essential, in combination with genome sequences and expression analysis, to address questions of pathogenicity and virulence, with the ultimate goal of the development of diagnostics, treatments and prevention strategies for the dermatophytes. PUBLIC HEALTH RELEVANCE: Dermatophytes are pathogenic fungi responsible for a variety of skin and nail infections, including athlete's foot and tinea capitis, a common fungal infection of the head in patients in socio- economically depressed areas. It is estimated that dermatophytes are the most common fungal infection worldwide. This proposal will develop a set of molecular tools that can be used in combination with the soon-to-be-completed genome sequences to address important questions about dermatophyte prevention, treatment and diagnosis.